Polyester resin exhibiting optical anisotropy in molten state and composition thereof

ABSTRACT

A polyester resin comprises 35 to 90 mole percent of the unit (I), 0.5 to 20 mole percent of the unit (II), 0.5 to 45 mole percent of the unit (III), 0.5 to 45 mole percent of the unit (IV), and 0.5 to 45 mole percent of the unit (V), exhibiting the anisotropy in its molten state. A polyester composition comprises the polyester resin as defined above and up to 95 percent by weight of an inorganic filler.

This invention relates to a polyester resin exhibiting opticalanisotropy in a molten state and having excellent heat resistance,processability and mechanical properties and its composition.

[Prior Art]

In recent years, various proposals have been made of a polymer (a liquidcrystal polymer) exhibiting optical anisotropy in a molten state as athermoplastic resin having a combination of heat resistance withprocessability. Representative examples thereof include those disclosedin (1) Japanese Patent Laid-Open No. 72393/1974, (2) Japanese PatentLaid-Open No. 43223/1975, and (3) Japanese Patent Laid-Open No.77691/1979. Each of these liquid crystal polymers contains a rigidmonomer introduced into the skeleton thereof to form a liquid crystalstructure, thereby realizing a high strength and excellentprocessability.

However, the following factors should be taken into consideration inorder to further improve the heat resistance and processability.Specifically, since a thermoplastic resin is usually molded at 350° C.at the highest and a special molding machine should be used when themolding is conducted at a temperature above 350° C., the moldingtemperature is preferably 350° C. or below from the viewpoint ofversatility in shaping and economy of heat source.

Further, there is an ever-increasing tendency of the thermoplastic resinto be used under severe conditions, and a particular importance isplaced on the reliability of the mechanical properties of the resin at ahigh temperature. Therefore, it is desired that the resin have a thermaldeformation temperature, serving as an indication of the heatresistance, of at least 150° C., preferably 200° C.

With respect to the thermoplastic resin, the two above-describedproperties are contradictory to each other, so that it is very difficultto simultaneously accomplish a lowering in the melting point orfluidizing point and an increase in the thermal deformation temperature.

Although the above-described conventional liquid crystal polymer (1)satisfies the requirement with respect to the thermal deformationtemperature, i.e., 200° C. or above, it does not satisfy the requirementwith respect to the molding temperature, i.e., 350° C. or below.Although the above-described conventional liquid crystal polymers (2)and (3) satisfy the requirement with respect to the molding temperature,i.e., 350° C. or below, the thermal deformation temperatures of liquidcrystal polymers (2) and (3) are 100° C. or below and 180° C.,respectively, and therefore are below the above-described desirablethermal deformation temperature range.

[SUMMARY OF THE INVENTION]

In view of the above-described circumstances, the present inventors havemade extensive and intensive studies with a view to developing athermoplastic resin which can simultaneously satisfy the propertiescontradictory to each other, i.e., heat resistance and highprocessability, and can exhibit excellent mechanical properties even insevere environments and, as a result, have found that a polyester havingparticular constituent units can solve the above-described problems andoffer a good balance among the properties, which has led to thecompletion of the present invention.

Specifically, the present invention relates to a polyester resinexhibiting optical anisotropy in a molten state, characterized bycomprising constituent units represented by the following formulae (I)to (v) as indispensible components in amounts of 35 to 90 % by mole, 0.5to 20% by mole, 0.5 to 45% by mole, 0.5 to 45% by mole, and 0.5 to 45%by mole, respectively: ##STR1##

The invention is, in other words, drawn to a polyester resin comprises35 to 90 mole percent of the unit (I), 0.5 to 20 mole percent of theunit (II), 0.5 to 45 mole percent of the unit (III), 0.5 to 45 molepercent of the unit (IV) and 0.5 to 45 mole percent of the unit (V),exhibiting the anisotropy in its molten state. The polyester compositioncomprises the polyester resin as defined above and up to 95 percent byweight of an inorganic filler.

The present invention enables a polymer having a good balance of highprocessability and heat resistance to be provided through a combinationof the above-described particular constituent units in particularproportions, particularly with a low content of constituent (II).

Specific examples of a compound for providing polymer constituent unit(I) include p-hydroxybenzoic acid and its derivatives. Examples of thederivatives include acylated benzoic acids such as acetoxybenzoic acid,benzoates such as methyl hydroxybenzoate, ethyl hydroxybenzoate, butylhydroxybenzoate and phenyl hydroxybenzoate, and acyl chlorides such ashydroxybenzoyl chloride.

Constituent unit (I) is used in an amount of 35 to 90% by mole,preferably 50 to 90% by mole based on the total amount of theconstituent units.

Specific examples of a compound for providing constituent (II) include2-hydroxy-6-naphthoic acid and its derivatives. Examples of thederivatives include acylated naphthoic acids such as2-acetoxy-6-naphthoic acid, naphthoates such as methyl2-hydroxy-6-naphthoate, ethyl 2-hydroxy-6-naphthoate, butyl2-hydroxy-6-naphthoate, and phenyl 2-hydroxy-6-naphthoate, and acylchlorides such as 2-hydroxy-6-naphthoyl chloride.

Constituent unit (II) is used in an amount of 0.5 to 20% by mole,preferably 1 to 15% by mole based on the total amount of the constituentunits. The incorporation of constituent unit (II) even in a small amounthas a great effect on the characteristics of the polymer.

Specific examples of a compound for providing constituent unit (III)include resorcinol and its derivatives. Examples of the derivativeinclude esters such as diacetoxyresorcinol.

Constituent unit (III) is used in an amount of 0.5 to 45%, preferably 2to 25% by mole based on the total amount of the constituent units.

Specific examples of a compound for providing constituent unit (IV)include hydroquinone and its derivatives. Examples of the derivativesinclude esters such as diacetoxyhydroquinone.

Constituent unit (IV) is used in an amount of 0.5 to 45% by mole,preferably 2 to 25% by mole based on the total amount of the constituentunits.

Specific examples of a compound for providing constituent unit (V)include terephthalic acid and/or isophthalic acid and their derivatives.Examples of the derivatives include phthalates such as methyl phthalate,ethyl phthalate and phenyl phthalate, and acyl chlorides such asphthaloyl chloride.

Constituent unit (V) is used in an amount of 0.5 to 45% by mole. Theamount of isophthalic acid is preferably 15% by mole or less.

The polymer of the present invention is prepared from these compounds bypolymerization such as direct polymerization or transesterification.Melt polymerization and slurry polymerization are usually employed forthe polymerization.

The above-described polymerization is conducted in the presence ofvarious catalysts, and representative examples of the catalyst includedialkyltin oxide, diaryltin oxide, titanium dioxide, alkoxytitaniumsilicate, titanium alcoholate, alkali metal carboxylate and alkalineearth metal carboxylate, and Lewis acid such as BF₃ .

The catalyst is used in an amount of usually about 0.001 to 1% byweight, particularly preferably 0.01 to 0.2% by weight based on thetotal weight of the monomers.

The polymer prepared by the above-described polymerization process canbe further heated in an inert gas to bring about solid polymerization tothereby increase the molecular weight.

That the polymer is a liquid crystal polymer exhibiting opticalanisotropy in a molten state is essential for the polyester resin of thepresent invention to have a combination of heat resistance with highprocessability.

The properties of the anisotropic melt phase may be examined by acustomary polariscopic method using crossed Nicol prisms. Moreparticularly, the presence of the anisotropic melt phase can beconfirmed by observing a sample placed on a Leitz hot stage in anitrogen atomosphere at a magnification of 40 under a Leitz polarizationmicroscope. The above-described polymer is optically anisotropic.Namely, when it is placed between crossed Nicol prisms, it transmitslight. If the sample is optically anisotropic, the polarized light canbe transmitted, even when it is in a static state.

In the present invention, the liquid crystallinity and melting point(liquid crystal development temperature) may be used as an indication ofthe processability. The flowability of a polymer in a molten state isdeeply concerned in whether or not the polymer exhibits liquidcrystallinity. The polyester of the present invention should exhibitliquid crystallinity in a molten state.

A nematic liquid crystalline polymer brings about a remarkable loweringin the viscosity at a temperature above the melting point. Therefore, inthis case, an indication of the processability is to exhibit liquidcrystallinity at or above the melting point thereof. For this reason,the melting point (liquid crystal development temperature) should bepreferably 350° C. or below from the viewpoint of heating capability ofgeneral molding machines.

In the present invention, the thermal deformation temperature, rigidityat a high temperature, etc. may be used as an indication of the heatresistance. With the consideration of the applications for the resin, itis necessary to satisfy the following heat resistance requirements: (1)the material has soldering heat resistance sufficient for withstandingthe step of soldering in the field of electricity or the like; and (2)the material can be continuously used under stress at a hightemperature. The above item (2) can be evaluated by using the thermaldeformation temperature, and although the performance of the resin perse correlates with the above-described item (1), it can be said thatwhen the thermal deformation temperature of the resin is 200° C. orabove, the resin has very excellent heat resistance when used as amaterial for parts associated with heat accumulators and heat sources.

Various inorganic and organic fillers in the fibrous, particulate orflaky form may be incorporated in the polyester of the present inventiondepending upon the purpose of the use.

Examples of the fibrous filler include inorganic fibrous materials suchas glass fiber, asbestos fiber, silica fiber, silica/alumina fiber,alumina fiber, zirconia fiber, boron nitride fiber, silicon nitridefiber, boron fiber, potassium titanate fiber, and fibrous materials ofmetals such as stainless steel, aluminum, titanium, copper, and brass.An especially representative fibrous filler is glass fiber. It is alsopossible to use high-melting organic fibrous materials such aspolyamide, fluororesin, polyester resin, or acrylic resin.

Examples of the particulate filler include carbon black, graphite,silica, quartz powder, glass beads, milled glass fiber, glass balloons,glass powder, silicates such as calcium silicate, aluminum silicate,kaolin, talc, clay, diatomaceous earth and wollastonite, metallic oxidessuch as iron oxide, titanium oxide, zinc oxide, antimony trioxide andalumina, metal carbonates such as calcium carbonate and magnesiumcarbonate, metal sulfates such as calcium sulfate and barium sulfate,and other various powdery metals such as ferrite, silicon carbide,silicon nitride and boron nitride.

Examples of the flaky inorganic material include mica, glass flake, andvarious metallic foils.

Examples of the organic filler include heat-resistant high strengthsynthetic fibers such as organic polyester fiber, liquid crystal polymerfiber, aromatic polyamide fiber, and polyimide fiber.

These inorganic and organic fillers may be used alone or in acombination of two or more of them. Combined use of the fibrous fillerand the particulate or flaky filler is preferable for the resin to havea combination of mechanical strengths with dimensional accuracy,electrical properties, etc. The inorganic filler is incorporated in anamount of 95 % by weight or less, preferably 1 to 80 % by weight basedon the total amount of the composition.

It is preferred that, if necessary, these fillers be used in combinationwith binders or surface treatments.

Further, the polyester of the present invention may contain otherthermoplastic resins as an auxiliary additive in such an amount as willnot spoil the purpose of the present invention.

The thermoplastic resin used in this case include polyolefins such aspolyethylene and polypropylene, aromatic polyesters comprising either anaromatic dicarboxylic acid and a diol, such as polyethyleneterephthalate and polybutylene terephthalate, or a hydroxy carboxylicacid, polyacetal (homopolymer and copolymer), polystyrene, polyvinylchloride, polyamide, polycarbonate, ABS, polyphenylene oxide,polyphenylene sulfide, and fluororesin. These thermoplastic resins maybe used in the form of a mixture of two or more of them.

[Effect of the Invention]

The organic polyester and its composition according to the presentinvention comprising particular constituent units and exhibiting opticalanisotropy in a molten state can exhibit excellent performance, isflowable at a processing temperature of 350° C. or below, can besubjected to usual injection molding, extrusion molding and compressionmolding, can be worked into various three-dimensional moldings, fibers,films, etc. and particularly can exhibit suitable flowability forinjection molding. Further, the organic polyester and its compositionaccording to the present invention can not only maintain the mechanicalstrengths even in a high temperature state because the thermaldeformation temperature is 200° C. or above but also has soldering heatresistance, which renders the organic polyester and its compositionsuitable for use in various applications where heat resistance isrequired.

[EXAMPLES]

The present invention will now be described with reference to thefollowing Examples which should not be construed as limiting the presentinvention.

The measuring methods used in the present invention will first bedescribed.

(1) Measurement of liquid crystallinity

The liquid crystallinity of the prepared resin was confirmed with aLeitz polarization microscope. Specifically, a sample placed on a Leitzhot stage was observed in a nitrogen atmosphere at a magnification of40. When the sample transmitted a light beam when placed between crossednicols, the sample was regarded as having a liquid crystal structure.

(2) Measurement of melting point

The melting point was measured with a differential scanning calorimeter.

(3) Measurement of soldering heat resistance

The soldering heat resistance was measured by immersing a specimen of 1mm cut out from a press sheet in a soldering bath of 260° C. for 30 secand observing the surface appearance. When any abnormal phenomenon, suchas blistering, wrinkling, cracking, or deformation, was observed on thesurface, the sample was evaluated as having poor soldering heatresistance (X), while when the surface was free from such abnormalphenomena, the sample was evaluated as having good soldering heatresistance (O).

(4) Measurement of torsional rigidity

The rigidity at 250° C. was measured with a Rheometer manufactured byRheometrics, Inc. with respect to a tensile specimen cut out from a 1mm-thick press sheet. The thermal deformation in the step of solderingor the like can be evaluated by the rigidity in a high-temperatureatmosphere. When the sample has a rigidity of at least 10⁴ dyn/cm² at250° to 260° C., it can be regarded as having excellent thermaldeformation resistance.

(5) Measurement of thermal deformation temperature

The thermal deformation temperature was measured according to ASTM-D 648(load: 18.6 kg/cm²).

EXAMPLE 1

A reactor equipped with an agitator, a nitrogen inlet, and a distillingtube was charged with 50% by mole of p-acetoxybenzoic acid, 5% by moleof 2,6-acetoxynaphthoic acid, 5% by mole of diacetoxyresorcinol, 17.5%by mole of diacetoxyhydroquinone, 22.5% by mole of terephthalic acidsand potassium acetate in an amount of 0.05% by weight based on the totalamount of the charge. The mixture was heated to raise the temperature to260° C. over a period of 1 hr in a nitrogen gas stream. The mixture wasthen heated at 260° to 300° C. for 2 hr while distilling formed aceticacid from the reactor, and then at 300° to 320° C. for 1 hr and at 320°to 350° C. for 1 hr. Formed acetic acid was distilled in vacuo. Nitrogenwas introduced into the reaction mixture to cool it to room temperature.The resultant polymer exhibited optical anisotropy at about 310° C. orabove when observed under a polarization hot stage microscope. Themelting temperature, thermal deformation temperature, and rigidity weremeasured respectively by the above-described methods. The results areshown in Table 1.

EXAMPLES 2 TO 4

Polymerization was conducted in substantially the same manner as that ofexample 1 by making use of the monomers in proportions shown in Table 1.The resultant polymers were subjected to measurements by the same methodas that of Example 1. The results are shown in Table 1.

EXAMPLE 5

A polymer was prepared in the same manner as that of Example 3, exceptthat isophthalic acid was used instead of terephthalic acid. The polymerwas subjected to measurements by the same method as that of Example 3.The results are shown in Table 1.

COMPARATIVE EXAMPLES 1 TO 3

Polymerization was conducted in the same manner as that of Example 1 bymaking use of the monomers in proportions shown in Table 1, and theresultant polymers were subjected to measurements by the same method asthat of Example 1. The results are shown in Table 1.

EXAMPLE 6

100 parts by weight of the polymer used in Example 2 was mixed with 15parts by weight of glass fibers to prepare a composition, and thecomposition was subjected to measurements in the same manner as that ofExample 1. The results are shown in Table 1.

                                      TABLE 1                                     __________________________________________________________________________    composition of polymer (mol %)                                                           2,6-acetoxy-        tere-                                              p-acetoxyben-                                                                        naphthoic                                                                           diacetoxy-                                                                          diacetoxy-                                                                            phthalic                                                                           isophthalic                                   zoic acid                                                                            acid  resorcinol                                                                          hydroquinone                                                                          acid acid  inorganic filler                    __________________________________________________________________________    Ex. 1                                                                             50     5     5     17.5    22.5 --    --                                  Ex. 2                                                                             70     5     2.5   10      12.5 --    --                                  Ex. 3                                                                             88     2     2     3       5    --    --                                  Ex. 4                                                                             70     5     2.5   10      10   2.5   --                                  Ex. 5                                                                             88     2     2     3       --   5     --                                  Comp.                                                                             90     --    3     3       5    --    --                                  Ex. 1                                                                         Comp.                                                                             30     25    5     17.5    22.5 --    --                                  Ex. 2                                                                         Comp.                                                                             65     25    2     3       5    --    --                                  Ex. 3                                                                         Ex. 6                                                                             70     5     2.5   10      12.5 --    15 pts. wt. glass fiber                                                       (based on 100 pts. wt.                                                        polymer)                            __________________________________________________________________________    properties of polymer or composition                                                              thermal                                                                       deforma-                                                                            solder-                                                          torsional                                                                            tion  ing heat                                                                           liquid                                              melting point                                                                         rigidity                                                                             temp. resist-                                                                            crystal-                                            (°C.)                                                                          (dyn/cm.sup.2)                                                                       (°C.)                                                                        ance linity                                                                            miscellaneous                              __________________________________________________________________________    Ex. 1                                                                              312     19,000 215   O    O                                              Ex. 2                                                                              335     21,000 220   O    O                                              Ex. 3                                                                              346     23,000 235   O    O                                              Ex. 4                                                                              330     20,000 220   O    O                                              Ex. 5                                                                              338     22,000 225   O    O                                              Comp.                                                                              378     --     --    --   O   no homogeneous polymer produced            Ex. 1                              because of formation of insolubles         Comp.                                                                              270      7,000 140   X    O                                              Ex. 2                                                                         Comp.                                                                              268      6,000 135   X    O                                              Ex. 3                                                                         Comp.                                                                              335     26,000 265   O    O                                              Ex. 6                                                                         __________________________________________________________________________

We claim:
 1. A polyester resin which comprises 35 to 90 mole percent ofthe unit (1), 0.5 to 20 mole percent of the unit (II), 0.5 to 45 molepercent of the unit (III), 0.5 to 45 mole percent of the unit (IV), and0.5 to 45 mole percent of the unit (V), exhibiting the anisotropy in itsmolten state: ##STR2##
 2. A polyester composition which comprises thepolyester resin as defined in claim 1 and an inorganic filler in anamount up to 95 percent by weight.
 3. A polyester resin exhibitingoptical anisotropy in the molten state according to claim 1 whichincludes 1 to 80 percent by weight of an inorganic filler.
 4. Apolyester resin exhibiting optical anisotropy in the molten stateaccording to claim 3 wherein said inorganic filler is a combination offibrous and particulate fillers.
 5. A polyester resin exhibiting opticalanisotropy in the molten state according to claim 1 wherein said resinis capable of being melt processed at a temperature of 350° C. or belowand is capable of forming articles which exhibit a thermal deformationtemperature of at least 200° C.
 6. A polyester resin exhibiting opticalanisotropy in the molten state according to claim 1 wherein said resinconsists essentially of 50 to 90 percent of unit (I), 1 to 15 molepercent of unit (II), 2 to 25 mole percent of unit (III), 2 to 15 molepercent of unit IV, and 0.5 to 45 mole percent of unit (V) with theproviso that any isophthaloyl units which are included in unit (V) beprovided in a concentration of no more than 15 mole percent.